The present invention relates to intraocular lenses and more specifically to a system for staking a haptic to an optic using a laser beam having a wavelength near the infrared region.
Various systems are currently being used for attaching haptics to optics to form intraocular lenses through staking. Some of these systems require that a radial bore be drilled into the optic, as well as, an axial bore from the optic upper surface intersecting the radial bore. An end portion of the haptic is then inserted into the optic through the radial bore until a portion of the inserted haptic is exposed through the axial bore. A heat source is then used to apply heat through the axial bore to melt the exposed haptic. After melting, the exposed haptic cools and coalesces into a bead, staking the haptic into the optic.
One current system for staking uses a Xenon photocoagulator as a heat source. The photocoagulator, which uses a Xenon arc lamp as a heat source, is an energy inefficient way of staking haptics to optics. When operating at peak output, the photocoagulator requires 5500 watts of power (220 VAC, 30 amps). Other systems use a Nd:YAG laser to transmit a laser beam through the axial bore to heat and melt the haptic. The Nd:YAG lasers, which operate in the infrared region at approximately a 1060 nm wavelength, are thermally efficient. However, when used for staking, their high thermal efficiency causes the haptic material to rapidly heat, resulting in nonuniform heating of the haptic. Nonuniform heating causes a weaker staking bond between the haptic and the optic. Furthermore, the Nd:YAG lasers are fairly expensive and require complex optics to deliver and focus the laser beam from the laser source onto the haptic. Due to the specialized optics, the operation of an Nd:YAG laser is also more complex resulting in operational errors and reducing the overall reliability of a staking process.
Lasers transmitting energy in the visible region of the spectrum (approximately 450-750 nm) are also being used for the staking process (U.S. Pat. No. 5,118,452). These lasers also require complex, expensive optics for their operation. Methods which use lasers transmitting energy in the visible range often require that the laser energy is coordinated with the color of the haptic to be attached. For example, if a blue haptic is to be attached, laser energy having a wavelength in the blue portion of the visible spectrum is used.
Some of the current methods used to stake the haptic to the optic require that an external piece of material is fused to the haptic. For example, the method disclosed in U.S. Pat. No. 5,118,452, requires that two intersecting bores be drilled on the periphery of the optic, wherein in one bore is inserted the haptic and in the other is inserted a separate anchor strand intersecting the haptic. A visible laser is then aimed at the intersection of the two bores fusing the strand to the haptic and, thus, staking the haptic to the optic.
Another method requiring the fusing of an external piece of material to the haptic is the method disclosed in U.S. Pat. No. 4,863,539. There the optic is swelled by being immersed in water and then an organic liquid, thereby, increasing the diameter of the peripheral and axial bores. After swelling, a haptic is inserted into a peripheral bore and a pin is inserted through the axial bore intersecting the inserted haptic. Afterwards, the organic liquid is removed and the optic contracts onto the haptic and pin. The pin is then heated and fused to the haptic.
Other methods of staking a haptic to an optic, such as the one disclosed in U.S. Pat. No. 4,104,339, require that the haptic comprise a wire. The wire haptic is inductively heated and simultaneously pressed into the optic, melting the optic material in the vicinity of the heated haptic and fusing the haptic to the optic. In another embodiment, bores are drilled on the periphery of the optic. The haptics are inserted into the bores. An inductively heated thin probe is then pushed through the base of the optic until it makes contact with the inserted haptic. The probes melts the optic and haptic material in its vicinity fusing the haptic to the optic.
To overcome the complexities associated with these methods, it is desirable to develop a system for staking a haptic to an optic that is highly reliable over an extended lifetime, that can use simple inexpensive optics, that is not required to be thermally efficient so as to allow for the controlled and uniform melting of the haptic to yield better uniformity and consistency, that does not require the use of laser energy having a wavelength in the visible region, that does not require a laser energy wavelength which is coordinated to the color of the haptic, that does not require the melting of an external piece of material for fusing the haptic to the optic, that does not require the swelling and subsequent reduction of the optic, and that does not require melting of the optic material.